S12ZVML 24V-system application use case question

[StanleyH]

Dear Sir,

  Our customer is using MC9S12ZVML for their HVAC blower project, and asks a question about 24V-system application use case. Hope you can help. Thanks.

  The system voltage is two 12V batteries in series which is possible high to 32V(16V+16V) when the battery is full. We found an AN5082 that suggests users to add a regulator for the Vsup and a gate driver for high & low side MOSFET.

  The customer ask how to deal with this pin, HD ?

  This pin shall keep under 20V and be required to close to the drain connections of the high-side MOSFET which is the battery voltage(36V possibly).

Where shall this pin, HD, connect to ?

Thanks.

Best regards,

Stanley

Message was edited by: Yao-Tsung Huang [ To cross out the power supply to be voltage regulator in the final image ]

[RadekS · Accepted solution]

Hi Stanley,

HD pin has to be connected behind external voltage regulator. We cannot connect more than 26V to HD pin - except short pulses (with no guarantee of function during this time).

In fact, In case of external gate driver, we do not use internal gate driver. Therefore note about required connection to close to the drain connections of the high-side MOSFET is not valid in this specific case.

I hope it helps you.

Have a great day,
RadekS

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[draganandric]

Hi Radek,

I am not sure if I understand your answer : Does it mean, in 24v application, S12ZVML have to use general I/O pins to generate PWM to external gate drivers ?

I am about to modify existing S12ZVML, 12v controller to 24v. The plan was to connect GDU PWM signals to gate driver ICs (one per phase) and omit the charge pump components. Also to connect 12v to internal PWM OP amps.

Is this doable?

Thanks,

Dragan

[RadekS]

Hi Dragan,

Yes, that is correct. The GDU in S12ZVM is designed only for 12V applications.

So, if you will use external GDU for 24V application, you should use PMF module directly for generating PWM signals to the external GDU. Yes, the PMF signals are available at port P and T.

The internal OP amps are powered by the internal voltage regulator in GDU module, but the range is only up to 5V.

I think that your concept will be rather too complicated.

Since most of the S12ZVM important features will be not used directly (internal voltage regulator, a main part of GDU,…), I would like to rather suggest to use general purpose MCU (powered from 3.3V or 5V) and external GDU unit for the 24V application.

For example: S32K MCU and MC34GD3000 pre-driver for PMSM motors

https://www.nxp.com/products/power-management/motor-drivers/h-bridges/3-phase-pmsm-development-kit-w...

other motor control kits:

https://www.nxp.com/support/developer-resources/hardware-development-tools/motor-control-development...

I hope it helps you.

Best regards

Radek

[draganandric]

HI Radek,

Thank  you for the clarification.

But I have seen that  MagniV is "advertised" for 24v application, as in below text. What does it mean "the key approach is to add selected external components that extend the devices's operational voltage range". Sounds like it should work if mosfets and capacitors are sized for higher voltage. 

[RadekS]

Hi Dragan,

The S12ZVM family was designed for 12V motor control applications.

The highest voltage for GDU is 26.6V (Note: Operation beyond 20V is limited to 1 hour over lifetime of the device).

When we add 12V for high N-channel MOSFET and margins, we are close to breakdown voltage for this 180nm technology.

So, you will need external gate driver for 24V motor control application.

Additionally, the typical load dump voltage for 24 systems is 60V – it means, that you also need overvoltage protection circuit.

There is application note AN5082 MagniV in 24V Applications:

http://www.nxp.com/files/microcontrollers/doc/app_note/AN5082.pdf

This application note mentions several topics which must be considered when we want use S12ZVM MCU for 24V applications.

I hope it helps you.

Best regards

Radek